Circuit interrupter



March 8, 1955 G, B, CUSH|NG 2,703,828

CIRCUIT INTERRUPTER Filed Jan. 25. 1950 2 Sheets-Sheet l Figi.

Figi. 3

WITNESSES: n INVENTOR I a`r George B. Cushing.

March 8, 1955 c. B. cUsHlNG l CIRCUIT INTERRUPTER 2 Sheets-Sheet 2 FiledJan.v 25. 195o lNvENToR George B Cushlng BY' d 7z//Jw ATToRN 8WITNESSES:

United States Patent CIRCUH INTERRUPTER George B. Cushing, Turtle Creek,Pa., assignor to Westmghouse Electric Corporation, East Pittsburgh, Pa.,a y corporation of Pennsylvania Application January 25, 1950, Serial No.140,491 21 Claims. (Cl. ZOU- 34) This invention relates to circuitinterrupters in general,

and, more particularly, to contact operating structures therefor. Ageneral object of my invention is to provide an improved high speed typeof circuit interrupter in which improved means are utilized to providethe necessary contact pressure in the closed circuit position, yetproviding extremely rapid opening separating motion or' the contactstructure during the opening operation.

Another object is to provide an improved circuit interrupter utilizingimproved movable dashpot means for providing the contact pressure in theclosed circuit position and enabling extremely early separating motionbetween the contact structure to be achieved during the openingoperation of the interrupter, without any time delay whatsoever.

Further objects and advantages will readily become apparent upon readingthe following speciication taken in conjunction with the drawings, inwhich:

Figure 1 is a side elevational view, partially in vertical section, ofan improved circuit interrupter embodying my invention and shown in theclosed circuit position;

Fig'. 2 is an enlarged vertical sectional view through the left-hand arcextinguishing unit of Fig. l, the contact structure being shown in theclosed circuit position;

Fig. 3 is a fragmentary vertical sectional view similar to that of Fig.2, but indicating the disposition of the parts at the beginning of theopening operation;

' Fig. 4 is a fragmentary vertical sectional view, similar to that ofFig.' 3, but showing the disposition of the contact parts at the end'ofthe opening operation;

Fig. 5 is an enlarged vertical sectional view through my improvedmovable dashpot means;

Fig. 6 is an enlarged fragmentary view taken along the line VI-VI ofFig. 2;

Fig. 7 is an enlarged fragmentary view, in vertical section, of amodified type movable dashpot means;

Fig.. 8 is a view taken along the line VII--VIII of Fig. 7, looking inthe direction of the arrows; and

Fig. 9 1s a diagrammatic view, in vertical section, of a modified typecircuit interrupter incorporating my invention, the contact structurebeing shown in the closed position.

Referring to the drawings, and more particularly to Fig. l thereof, thereference numeral 1 designates a tank filled to the level 2 with asuitable arc extinguishing liquid 3, in this instance, circuit breakeroil. Depending from the cover 4 of the tank 1 is a pair of terminalbushings 5, 6, to the lower ends of which are appended identical arcextinguishing units, generally designated by the reference character 7.

The arc extinguishing units 7 are electrically interconnected in theclosed circuit position of the interrupter as shown in Fig. l, by aconducting cross-bar or conducting movable member 8 actuated verticallyin a reciprocal manner by an insulating lift rod 9. The lift rod 9 isconnected to a suitable operating mechanism, not shown, which forms nopart of my invention.

Referring to Fig. 2, which more clearly shows the internal constructionof the arc extinguishing unit 7, it will be noted that I have providedsuitable contact structure, generally designated by the referencecharacter 10, and including a pressure-generating contact 11, anintermediate contact 12 and a lower movable interrupting contact 13. Themovable interrupting contact 13 is carried at the extremity of thecross-bar or movable member 8.

The pressure-generating contact 11 is pivotally connected, as at 14, toa link.15, the latter being pivoted at a stationary pivot 16. The pivotpin 16 is journalled f"ice in the upper casting wall 17 of thepressure-generating chamber 18. The right-hand end of thepressure-generating contact 11 is bit'urcated, as shown, and forms twolegs 19. The pin i4 passes through both legs 19.

The right-hand ends of the legs 19 of the pressuregenerating contact 11are pivotally connected to a pair of bosses 20, the latter jutnngoutwardly from a piston 21. The piston 21 slides within a piston chamber22, tormlng, collectively with the piston 21, a movable dashpot means,generally designated by the reference character 23. rl`he piston chamber22 and the piston member 2l constitute a pair of relatively movableparts.

The upper end 24 of the movable dashpot means 23 has venting means 25associated therewith including apertures or huid-inlet means 26 providedin the upper end wall 27 of the piston chamber 22. The apertures 26 arein communication with additional apertures 28 constituting a part of theventing means 25.

l provide valve means, generally designated by the reference character29, associated with the venting means 25 and constituting a valve plate30. l provide biasing means '31, in this instance including acompression spring, which biases the valve means 29 to its upper closedposition over the apertures 26. rl`he compression spring 31 seats at itsupper end upon the valve plate 30, and seats at its lower end upon aspider stop 32 integrally formed with the piston chamber 22. The movablepiston chamber 22 is threadedly connected, as at 34 to an insulatingoperating member 35.

The insulating operating rod or member 35 is biased downwardly by anaccelerating spring 36, the upper end of which seats against the lowerplate 37 of the unit 7. The lower end ot the compression spring 36 seatsagainst a cap 33 integrally formed with the side operating rod 35. ltwill, therefore, be observed that the side operating rod 35 is biaseddownwardly into abutting engagement with the cross-bar 8, and is movedupwardly thereby duringthe closing operation in opposition to thebiasing action exerted by the compression spring 36.

in the closed circuit position of the interrupter as shown by the fulllines in Fig. l and also in Fig. 2, the electrical circuit therethroughincludes terminal stud 39, clamp 40, top dome casting 41, flexible strap42, pressure-generating contact 11, intermediate contact 12, lowermovable interrupting contact 13 and through the conducting cross-bar 8to the right-hand unit 7. The electrical circuit extends through theright-hand unit 7 in a similar manner to its passage through theleft-hand uint 7.

During the opening operation, suitable mechanism, not shown, but whichmay be operated manually and which is responsive to overload conditionsexisting in the controlled circuit, operates to cause downward openingmovement of the insualting lift rod 9. The downward opening motion ofthe litt rod 9 carries the crossbar 8 and lower movable interruptingcontacts 13 therewith. The downward motion of cross-bar 8 permits theaccelerating spring 36 to force the operating rod 35- downwardly withthe cross-bar 8.

An important feature ol` my invention is the fact that during theinitial portion of the opening operation the bosses 20, piston 21 andpressure contact 11 move immediately with the operating rod 35. Inprevious constructions, the contact biasing spring 43 was permitted toexpand during the initial portion of the opening operation so that noopening movement whatsoever of the pressure-generating contact 11 tookplace until the wiping motion was taken up. In other words, in priorconstructions, contact pressure between the several contacts was broughtabout by a compression spring 43 and a lost-motion connection betweenbosses 20 and the operating rod 35, so that at the end of the closingstroke theoperating rod 35 could move upwardly relative to the bosses 20and pressure contact 11, thereby compressing the contact pressure spring43 to bring about the desired contact pressure between the severalcontacts 1li, 12 and 13.

During the initial portion of the opening operation, in such prior artstructures, the lost-motion between the bosses 20 and operating rod 35would have to be taken up before the operating rod 35 caused downwardmotion of the legs 19 and hence clockwise rotative opening motion of thepressure contact 11 away from the intermediate contact 12 to draw apressure arc therebetween. Consequently,v the dissipation of thelost-motion connection between the pressure-generating contact 11 andthe side operating rod 35 caused a delay in the separation of thecontacts 11,- 12, and this delay was undesirable for high speedoperation. In my invention I eliminate any such delay, or time necessaryto take up lost-motion between the legs 19 and the operating rod 35, bytrapping oil within the upper end 24 of the movable dashpot means 23.This slug of oil trapped at the upper end of the movable dashpot means23 causes the spring 43 to remain compressed at the initial portion ofthe opening operation so that the pressure contact 11 immediatelyseparates from the intermediate contact 12 at the tirst instant ofdownward opening motion of the side operating rod 35, as permitted bydownward opening motion of the cross-bar 8.

Fig. 3 shows the relative position of the parts at the end of theinitial portion of the opening operation when a shoulder 44 on thepiston chamber 22 has struck a stop 45 formed by the casting 41. It willbe noted that at this intermediate point in the opening operation stillthe slug of oil disposed in the region 46 above the piston 21 is trappedtherein, causing the piston 2 1 to immediately move downwardly with theinitial downward motion of the operating rod 35. A pressure-generatingarc 47 is drawn between the pressuregenerating contact 11 and theintermediate contact 12 within the pressure-generating chamber 18.

Fig. 4 shows the conditionlater at the end of the opening operation whenthe slug of oil has had a chance to leak past the piston21 to the lowerend of the piston chamber 22. It will ybe observed that the distance Din Fig. 4 is less than the distance D1 in Fig. 3 as a result of anextension of the contact compression spring 43 relative to its positionin Figs. 2 and 3. As shown, the piston 21 moves upwardly to the stopprovided by a spider 32.

The interrupting structure which utilizes the pressure generated at thepressure-generating arc 47 to create an oil ow to effect extinction ofthe interrupting arc, not shown, which is established between theintermediate and interrupting contacts 12, 13 forms no part of rnylinvention. Reference may be had for the details of the plate structureto U. S. Patent 2,467,760, issued April 19, 1949, to Leon R. Ludwig,Benjamin P. Baker and Winthrop M. Leeds and assigned to the assignee ofthe instant application. It suces to state that in the interruptingchamber 48 there are three types of plates used, an inlet plate 49 whichpermits the entrance of oil into the interrupting passage 48 from thevertical flow passages 50 leading to' the pressure-generating chamber18'. The oil passing through pairs of inlet passages 51 passes throughorifices 52 provided in orifice plates 5'3 and exhausts out of the unit7 through laterally eX'- fending vent passages 54 formed by the lateralseparation of two half plates 55, 5 6. For further details, referencemay be had to' the foregoing patent, but as mentioned previously, suchdetails form no part of my invention. it merely' being necessary' toknow that I form two serially related arcs, a pressure-generating arc 47between the contacts 11. 12 and an interrupting arc between the contacts12, 13, and that oil is driven by the' pressure are 47 downwardly awayfrom the pressure-generating chamber 18 through the two vertical flowpassages 50 into the interrupting passage 48, against the interruptingarc, not shown, and out of the unit 7 by means of the vent passages 54.

In the fully open circuit position, as shown by the dotted lines 57 ofFig. 1, it will be observed that the cross-bar 8 withdraws the contacts13 completely out of the units 7, and that also separation takes placebetween the cross-bar 8 and the caps 38 at the lower ends of the sideoperating rods 35.

During the closing operation the litt rod 9 moves the cross-bar 8 andcontacts 13 upwardly. The contacts 13 enter the units 7, andthecross-bar 8 strikes the caps 38 of operating rods 35 in abuttingengagement to carry the latter upwardly therewith. At this time thepiston 21 is at the upper end of the movable dashpot means 23 againstthe stop spider 32, as shown in Fig. 4 the contact compression spring 43being extended.

The lower movable interrupting contact 13 strikes the intermediatecontact 12 before the pressure-generating contact 11 strikes theintermediate contact'l2, raising the intermediate contact 12 slightlyupwardly against the biasing actionof the compression spring 58. Furtherupward motion of the cross-bar 8, movable contact 13 and operating rod35 takes place compressing the contact compression spring 43 and drawingoil within the chamber 46 past the valve means 29.

During this final portionof the closing operation, as mentioned, thecompression spring 43 is compressed thereby providing the requisitecontact presstir'e between the several contacts 11, 12 and 13 so thatupon halting of the upward closing motion of the cross-bar 8 the thecontact structure 10 and the movable dashpo't means 23 assume theposition as shown in Figs. 2', 5 and 6. 'j'

From the foregoing description of an operation of my invention, it willbe apparent that I have provided improved means for immediately causingseparating ino'- tion between the contacts l11, 12 at the start of thedown-l ward motion of the operatingl rod 35,` even before eittension ofthe contact pressure springv 43 oceiirs. This establishment of thepressure-generating arc 47 inA my improved interrupter before that ofthe prior rt'- structures lowers the interrupting time of the interrptersince the pressure-generating arc 47 is thereby established earlier thanthe pressure-'generating arc of the prior art structures. Furthermore,-I provide a Contact pressure spring 43 which functions in the samemanner as in' prior art structures to provide the requisite contactpressare between the several contacts in the closed position. However,unlike the prior art structures, my invention operates to avoid any timedelay, or the take up of lost-motion betweenthe operating rod 35 andpressuregenerating contact 11 at the beginning of the opening`operation.l

As a result, my inventionhas all the advantages of the prior artstructures in providing a contact compression spring 43, which iscompressed during the final portion of the closing operation, but myinvention does not have the disadvantage of necessitating the taking upof lost-motion between the pressure contact 11vand the side operatingrod 3510 delay the formation of the pressure-generating arc 47. With myvinvention immediate establishment of the pressure arc 47 results uponinitial downward motion of the operating Arod 3S by the use of themovable dashpot means 23A which I have provided. The result is a tasthigh speed interr'upter in which the pressure and interrupting arcs are.established immediately upon initial downward motion of the cross-bar 8andoperatingrod 35.

In certain instances, it may be desirable to interchange thepressure-generating and interruptingarcs, so that instead of the`pressure-generating arc 47 being established at the contacts 11, 12, itmay be established between the contacts 12, I3. In such event, theinterrupting arc might be established between the contacts 11, 12', theorder merely being inverted. Naturally, m invention .is applicable tosu'ch an arrangement in w ich it ijs desirable to establish theinterrupting arc at the top of the unit 7 between the contacts 11, 12rather than at the lower end of the unit 7, as shown in the foregoingembodiment of. my; invention.

Figs. 7 and 8' collectively show a modified form of movable dashpotmeans, generallyl designated by thereference character 59 and includinga piston 60 and a pis'- ton chamber 61. The operating rod 35 isthreadedly connected, as at 34, to lthe piston 60. The legs 19 of thebifurcated pressure-generatingContact 11 are pivotally mounted uponvbosses 62 integrally formed with the piston chamberol. A Contactycompression spring 63 isy disposed at' the upper end of the pistonchamber61,fasA showman'd biases the piston 60 downwardly. I providevalve means, generally designated by'thereference character 64,controlling the eiiit of liquid, in this instance', oil, out of theregion 65 above the piston' 60.

The valve means 46 4 includes a ball v'alv'e 66 closing an aperture 67provided centrally throngh thepis'tojn 60 and communicating with apassage 68 drilled throiigti the' extension 69 of the piston 6p. Asecond passage 1411's formed Within the extension 71. the latte'= b'eigthede'd to the upper end of the operating rod 35.

It willA Be noted that the piston chamber 61 is substam s, tiallyVcompletely enclosed, there being no necessity for 'cil .entering or:leaving the piston chamber 61- sine the diameter of the extension 69 isthe same as the diameter of the extension 71 and operating rod 35. c

The operation of this form of my invention will now be described. Themodified movable dashpot means 59 1s shown in Figs. 7 and 8 in theclosed circuit position of the interrupter (see Fig. 2) with the contactcompression spring 63 providing the contact pressure between the severalcontacts 11, 12 and 13. Oil completely lls the dashpot means 59, and theball valve 66 closes the aperture 67 as shown.

During the opening operation of the interrupter, at the iirst instant ofdownward opening motion of the operating rod 35, as permitted bylowering of the contact member 8, the entire movable dashpot means 59immediately moves downwardly with the operating rod 35. This resultsbecause of the oil trapped within the region 72 at the lower end of thepiston chamber 61. As a result, the initial downward opening motion ofthe operating rod 35 causes instant downward motion of the pistonchamber 61 immediately causing opening rotative motion of thepressure-generating Contact 11. Consequently, a pressure-generating arc47 is immediately established. lnterruption follows in a mannerpreviously described and leakage of oil around the periphery of thepiston 60 permits the contact compression spring 63 to force the pistonchamber 61 upwardly relative to the operating rod, 35, which at thistime has been halted, and the result is slight closing motion of thepressure-generating contact 1I t0 the distance D, as shown in Fig. 4.The interrupter now is in the fully open circuit disconnect position, asshown by the dotted lines 57 of Fig. l.

During the closing operation, the upward closing movement of the contactmember 8 picks up the operating rod 35 in a manner previously describedand causes reclosure of the contacts 11, 12 and 13 with the piston 60freely moving upwardly within the piston chamber 61 by the opening ofthe valve means 64 and a consequent rapid passing of oil through thepassage 68, aperture 67 and through the second passage 70 to the region72 within the piston chamber 61. pression spring 63 is easily compressedwith the free passage of oil past the valve means 64 and the breaker isin the closed position, with the requisite contact pressure beingprovided between the several contacts 11, 12 and 13 bythe compression ofthe contact compression spring The foregoing modification, asillustrated in Figs. 7 and 8, shows how I have interchanged the parts sothat instead of the pressure-generating contact 11 being connected tothe piston 21, it is connected to the piston chamber 61. Instead of theoperating rod 35 being connected to a piston chamber 22, it is connectedto the piston 6i). A complete interchange of the dashpot parts relativeto the pressure contact 1l and the operating rod 35 has consequentlybeen made in the embodiment of my invention shown in Figs. 7 and 8.

Fig. 9 shows a modified type of arc extinguishing unit generallydesignated by the reference character 74. In this embodiment, thepressure-generating arc is established between a lower movable pressurecontact 75 and a rigidly stationary intermediate contact 76. Theinterrupting arc is established between the rigidly stationaryintermediate contact 76 and an upper movable interrupting contact 77.The interrupting chamber 48 is vented by means of the plurality of vents79 extending out of the unit 74, and the passage of oil during aninterrupting operation is as indicated by the arrows of Fig. 9.

The side operating rod 35 may be connected by a movable dashpot means 23to a rotatable lever S0, the lefthand end of which is pivotali'yconnected, as at 81, to an actuating lever 82. The actuating lever S2 ispivotally connected, as at 83, to the upper end of the movableinterrupting contact 77 The left-hand end of the actuating lever 82, asviewed in Fig. 9, is connected to a roller 84 which slides in astationary raceway 85. The lever 80 is pivotally connected at 86 to astationary pivot as provided by a stationary bracket 37.

The lower movable pressure-generating contact 75 is pivotally connected,as at 88, to an actuating arm 89, the right-hand end of which ispivotally connected, as at 90, to a link 91, the upper end of which ispivotallyconnected at a stationary pivot 92. The actuating arm 89 ispivotally connected, as at 62, to a movable dashpot means 59.

As a result, the contact com- The operating rod 35 is biased downwardly,as in Fig. 2, by an accelerating compression spring 36. ln the closedcircuit position, as shown in Fig. 9, the contact pressure between thecontacts 76 and 75 is provided by the contact compression spring 63within the movable dashpot means 59. The contact pressure between thecontacts 76, 77

is provided by the contact compression spring 43 dis-l intermediatecontact 76 to draw an interrupting arc, not.

shown. At the same time, the lower movable pressure generating contact75 moves downwardly away from the rigidly mounted intermediate contact76 to establish a pressure-generating arc 47. Liquid ow takes place asindicated by the arrows of Fig. 9, and extinction of the interruptingarc takes place. Subsequently, the contact member 8 separates from theconducting cap 94 to provide a disconnect gap into the circuit.Following extinction of the arc, the contact compression springs 43, 63ot' the dashpots 23, 59, respectively, extend to slightly shorten thepressure-generating and interrupting gaps in a manner previouslydescribed.

During the closing operation, the contact member 8 moves upwardly, picksup the conducting cap 94 and hence the operating rod 35, to move thecontact structure to the closed position, the contact pressure beingprovided by the Contact compression springs 43, 63 of the movabledashpot means 23, 59, respectively.

This embodiment, as shown in Fig. 9, describes the flexibility andinterchangeability of the movable dashpot means 23, 59. It shows thatwherever a contact compression is desired with immediate opening motion.

of the contact with the initial opening movement of the contactoperating mechanism, in such a case my im-l slight clearance, the pistonchamber and the piston con-` stituting a pair of relatively movableparts, means at all time connecting one of the contacts with one of theparts, an operating member for opening and closing the contactstructure, means movably connecting the operating member with the otherof said parts, and valve means associated with the movable dashpot meansto trap liquid within the movable piston chamber so that during theinitial portion of the opening operation the movable piston chamber andthe piston move together as a unit in the same direction.

2. A circuit interrupter including a pressure-generating contact, anintermediate contact and a movable in` terrupting contact, thepressure-generating contact and the intermediate contact beingcooperable to establish a pressure-generating arc, the intermediatecontact and the movable interrupting contact being cooperable toestablish a serially related interrupting arc, a movable member whichcarries the movable interrupting contact, an operating member makingabutting engagement with the movable member at least near the end of theclosing operation, movable dashpot means including a movable pistonchamber and a piston movable therein with only slight clearance, thepiston chamber and the piston constituting a pair of relatively movableparts, means at all times connecting the pressure-generating contactwith,

one of the parts, means connecting the operating mem.-

ber with the other of said parts, and valve means associated with themovable dashpot means to trap liquid within the movable piston chamberso that during the initial portion of the opening operation the movable`piston chamber and the piston move together as a unit in the samedirection.

.3.; A. circuitvtinterrupter.including :a pressurevgeneratingcontact,Jan -intermediate contact and iav movable. m-

terrupting contact, the pressureggenerating .contactand thellintermediate .contact .being cooperable to )esablish apressuregeneratingfarc, the .intermediate contact and the movablev.interrupting contactfbeing cooperable to establishna :serially relatedinterrupting arc, .a movable member which carries the -movableinterrupting contact, an operatingvmember.;making abuttingengagementwith the movablemember :at leastnearthe end-of the closing.operation, movable dashpot Ymeans including. av movable piston chamberand a piston movable therein with only slight .clearancqthe pistonchamber and -the piston constituting ,a pair of yrelatively movableparts, .means at alltimesonnecting the .pressure-generating contact withoneof the parts, lmeans connecting the operat'ingmemberl with the otherof said parts, means biasing the piston toward one .end of the pistonchamber, huid-.inlet means-for .thepiston chamber :adjacent said one endof the piston chamber, `vand valve means associated with the movabledashpotmeansto trap liquid Within the movable ,pistonchamber so thatduring theinitial portion lof the .opening operation the-.movable.piston chamber and.

the .pistonmove together asaunit inthe same direction.

'4. A circuit interrupter including a fpressure-'generating contact, anintermediate contact and a movable interrupting contact, thepressure-generating contact and the intermediate contact beingcooperable to establish a pressure-generating arc, the intermediatecontact and the .movable interrupting contact being cooperable toestablish a serially related. interrupting arc, a movable member whichcarries the movable interrupting contact, an-operating membermakingabutting engagement with the movable member at least near the end of theclosing operation, .movable dashpot means including a movable pistonchamber and a piston movable therein with only slight clearance, thepiston chamber and the Vpiston constituting a pair of relatively movableparts, means interconnecting at .all times the pressurefgeneratingcontact with one of the parts, means Vconnecting the operating memberwith the other of said parts, means biasing the piston toward one .endof the piston chamber, `lluidinlet means for the piston chambervadjacent said `one end of the piston chamber, .and valvemeanscontrolling sai'duid-inlet means.

5. A circuit @interrupter Yincluding .contact structure comprising apair of relativelymovable cooperable contacts, movable dashpot meansincluding a movablepiston .chamber and a piston :movable .therein -withonly slight clearance, means at all times connecting 'one .of thecontacts `with .the `movable piston chamber, an operating member Vfor.opening and closing the contact structure. and means at all Atimesconnecting the operating member with .the piston.

k6. A circuit interrupter including contact structure comprising apairof relatively movable cooperablecontacts, movable dashpotmeansincludinga movablepiston vchamber and a piston movable therein with konly slight clearance. .means at all times connecting one .of the'contacts with the movable piston chamber, an `operating .member Aforopening andclosing the contact structure, means at all times connectingtheoperating member with the piston, and means biasing the piston towardone end ofthe pistonchamber. '7. A circuit interrupter including apressure-generating contact, an intermediate contact and a movable'interrupting contact, the pressure-generating contact and theLintermediate contact being .cooperable to establish apressure-generating.arc,.the intermediate contact and themovablesinterrupting ,contact being cooperable to establishaserially.related'interrupting arc, a movable membei'. Which.,carriesthe `.movable interrupting contact, an operating member making abuttingengagement with the movable member-at least near the end of thetclosingoperation, movable 'dashpot .means including amovable piston lchamberandV a `piston movable therein with only slight-"clearance, means .at.all `times .connecting vthe pressurefgenerating contact with vthe.movable pistonA chamber, `and means at all times connecting the'operating member with .the ,pi ston.

l8'. A circuit .interrnpter including :contact structure comprising apair of .relativelymovable cooperable contacts, movable dashpotmeansincluding a .movable pis.- ton' vchamber 'and a piston movable therein,.the-,piston necting the operating memberv with the other yof .said

parts, vmeans biasingone of saidipairof relatively movableupartsina-direction tending to close the contacts under pressure, and one-wayacting valve means .hlndermg motion of thefpiston within the pistonchamber Vin theopposite direction.

A circuit interrupter including contact structure comprising a pair ofrelatively movable cooperable contacts, movable dashpot means including`amovable piston chamber .and .a -piston movable therein with onlyslight clearance, the piston chamberand thepiston constituting apair ofrelativelymovable parts, `means at all times connecting one `of Athe,contacts with one of .the parts, an operating member for opening andclosing the contact structure, means movably connecting the operatingmember with the otherof said parts, a spring biasing the .piston towardone end of .the piston chamber, and 'valve means associated with themovable das'hpot means to trap liquid within the movable vpiston chamberso that .during the initialportionio'f the opening operationthe movablepiston chamber and .the pistonmove together as a unit in the samedirection.

.10. A circuit interrupter including contact .structure comprising apair .of relativelymovable cooperable contacts, movable dashpotmeansincluding a movable piston chamber and a--piston movable thereinwith only slight clearance, the piston chamber and the.pistonconstituting a pair of vrelatively movable parts,.means atallztimes connecting .one of the contacts with one of theparts, anoperating member for opening and closing thecontact structure,meansmovably connecting theoperating member with the other of saidparts, a .spring biasing the piston toward one endof the piston chamber,andoneway acting valveineans permitting relatively free motion of thepiston toward one endof the piston chamber but hindering. motionot the.piston toward the opposite `end of thepiston chamber.

1l. A circuit .interrupter .including :Contact vstructure comprising vapair ofrelatively ,movable cooperable-contacts, movable dashpot meansincludinga movablefpiston chamber and a piston movable therein withlonly slight clearance, the piston chamber and the piston constituting apair of relatively movableparts, means at all times connecting .one ofthe contacts with one of the parts, lan operating member for opening andclosing-the contact structure, means .movably connecting the operatingmember with the other of said parts., a spring biasing the piston.towardone end of the piston chamber, vfluid-.inlet meansfor'thepistonchamber disposed adjacent said end of. the piston chamber, and valvemeans associated with the movable dashpot means to trap liquid Withinthe movable piston chamber so that during the. initialportion ofthe.opening operation the movable piston chamber and the piston movetogether as a unit inthe same direction.

V12. .A circuit interrupter including contact structure comprising apair of relatively movable cooperable .con-V tacts,.movable dashpotmeans including a movable piston chamber and a piston movable thereinwith only vslight clearance, the piston chamber and the pistonconstituting a pair of relatively movable parts,.means at .alltimcsconnecting .one of the .contacts with one of the parts, an operatingmember for opening and closing the contact structure, means movablyconnecting the operating member with the other of said parts, a springbiasing the piston 'toward one end of the piston chamber, fluid-inletmeans for the piston chamber disposed adjacent said end of the pistonchamber, and one-Way-acting valve means controlling said fluid-inletmeans.

13. A circuit interrupter including contact structure comprisinga `pairof relatively movable cooperable contacts, movable dashpot meansincluding-amovable piston.

connectingone ot the contacts with one oi` the parts, au`

operating member for 'opening and closing the contactstructure,.meansmovably connecting the operating .mem-..

berv with the other of said parts, ,fluid-.inlet means.: for

the piston chamber disposed adjacent one end fof-:the

piston chamber, and valve means associated with the movable dashpotmeans to trap liquid within the movable piston chamber so that duringthe initial portion of the opening operation the movable piston chamberand the piston move together as a unit in the same direction.

14. A circuit interrupter including contact structure comprising a pairof relatively movable cooperable contacts, movable dashpot meansincludingI a movable piston chamber and a piston movable therein withonly slight clearance, the piston chamber and the piston constituting apair of relatively movable parts, means at all times connecting one ofthe contacts with one of the parts, an

operating member for opening and closing the contact` structure, meansmovably connecting the operating member with the other of said parts,fluid-inlet means for the piston chamber disposed adjacent one end ofthe piston chamber, and one-way-acting valve means controlling saiduid-inlet means.

l5. A circuit interruptor including contact structure comprising a pairof relatively movable cooperable contacts, movable dashpot meansincluding a movable piston chamber and a piston movable therein withonly slight clearance, the piston chamber and the piston constituting apair of relatively movable parts, means at all times connecting one ofthe contacts with one of the parts, an operating member for opening andclosing the contact structure, means movably connecting the operatingmember with the other of said parts, a spring biasing the piston towardone end of the piston chamber, iiuid-inlet means for the piston chamberdisposed adjacent said end of the piston chamber, one-way-acting valvemeans controlling said fluid-inlet means, and means biasing theone-Way-acting valve means to the closed position over the fluid-inletmeans, and valve means associated with the movable dashpot means to trapliquid within the movable piston chamber so that during the initialportion of the opening operation the movable piston chamber and thepiston move together as a unit in the same direction.

16. A circuit interrupter including contact structure comprising a pairof relatively movable cooperable contacts, movable dashpot meansincluding a movable piston chamber and a piston movable therein withonly slight clearance, the piston chamber and the piston constituting apair of relatively movable parts, means at all times connecting one ofthe contacts with one of the parts, an operating member ttor opening andclosing the contact structure, means movably connecting the operatingmember with the other of said parts, spring means biasing one of saidpair of relatively movable parts with respect to the other of said pairof relatively movable parts, means for actuating the operating member tocause closure of the contact structure, said spring means tending in theclosed circuit position of the interruptor to maintain the contactsclosed under spring pressure, and valve means associated with themovable dashpot means to trap liquid Within the movable piston chamberso that during the initial portion of the opening operation the movablepiston chamber and the piston move together as a unit in the samedirection.

17. A circuit interruptor including contact structure comprising a pairof relatively movable cooperable contacts, movable dashpot meansincluding a movable piston chamber and a piston movable therein withonly slight clearance, the piston chamber and the piston constituting apair of relatively movable parts, means at all times connecting one ofthe contacts with one of the parts, an operating member for opening andclosing the contact structure, means movably connecting the operatingmember with the other of said parts, spring means biasing one of saidpair of relatively movable parts with respect to the other of said pairof relatively movable parts, means for actuating the operating member tocause closure of the contact structure, said spring means tending in theclosed circuit position of the interruptor to maintain the contactsclosed under spring pressure, fluid-inlet means for the piston chamberdisposed adjacent one end of the piston chamber, and valve meansassociated with the movable dashpot means to trap liquid within themovable piston chamber so that during the initial portion of the openingoperation the movable piston chamber and the piston move together as aunit in the same direction.

18. A circuit interrupter including contact structure comprising a pairof relatively movable cooperable contacts, movable dashpot meansincluding a movable piston chamber and a piston movable therein withonly slight clearance, the piston chamber and the piston constituting apair of relatively movable parts, means at all times connecting one ofthe contacts with one or the parts, an operating member for opening andclosing the contact structure, means movably connecting the operatingmember with the other of said parts, and the piston and piston chambermoving together during the initial portion of the opening operation toseparate the contact structure.

19. A circuit interrupter including a pressure-generating contact, anintermediate contact and a movable interrupting contact, thepressure-generating contact and the intermediate contact beingcooperable to establish a pressure-generating arc, the intermediatecontact and the movable interrupting contact being cooperable toestablish a serially related interrupting arc, a movable member whichcarries the movable interrupting contact, an operating member makingabutting engagement with the movable member at least near the end of theclosing operation, movable dashpot means including a movable piston tchamber and a piston movable therein with only slight clearance, thepiston chamber and the piston constituting a pair of relatively movableparts, means at all times connecting the pressure-generating contactwith one of the parts, means connecting the operating member with theother of said parts, and the piston and piston chamber moving togetherduring the initial portion of the opening operation to separate thepressure-generating and intermediate contacts.

20. A circuit interrupter including a pressure-generating contact, anintermediate contact and a movable interrupting contact, thepressure-generating contact and the intermediate contact beingcooperable to establish a pressuregenerating arc, the intermediatecontact and the movable interrupting contact being cooperable toestablish a serially related interrupting arc, a movable member whichcarries the movable interrupting contact, an operating member makingabutting engagement with the movable member at least near the end of theclosing operation, movable dashpot means including a movable pistonchamber and a piston movable therein with only slight clearance, thepiston chamber and the piston constituting a pair of relatively movableparts, means at all times connecting the pressure-generating contactwith one of the parts, means connecting the operating member with theother of said parts, means biasing the piston toward one end of thepiston chamber, fluid-inlet means for the piston chamber adjacent saidone end of the piston chamber, and the piston and piston chamber movingtogether during the initial portion of the opening operation to separatethe pressure-generating and intermediate contacts.

21. A circuit interrupter including a pressure-generating contact, anintermediate contact and a movable interrupting contact, thepressure-generating contact and the intermediate contact beingcooperable to establish a pressure-generating arc, the intermediatecontact and the movable interrupting contact being cooperable toestablish a serially related interrupting arc, a movable member whichcarries the movable interrupting contact, an operating member makingabutting engagement with the movable member at least near the end of theclosing operation, movable dashpot means including a movable pistonchamber and a piston movable therein with only slight clearance, thepiston chamber and the piston constituting a pair of relatively movableparts, means interconnecting at all times the pressure-generatingcontact with one of the parts, means connecting the operating memberwith the other of said parts, means biasing the piston toward one end ofthe piston chamber, fluid-inlet means for the piston chamber adjacentsaid one end of the piston chamber, valve means controlling saidfluid-inlet means, and the piston and piston chamber moving togetherduring the initial portion of the opening operation to separate thepressuregenerating and intermediate contacts.

References Cited in the file of this patent UNITED STATES PATENTS2,422,569 Leeds June 17, 1947 2,530,952 Fry Nov. 2l, 1950 FOREIGNPATENTS 486,050 Great Britain May 30, 1938 640,009 Germany Dec. 2l, 1936

